How come there is visible light in Uv lights?

In summary, the conversation discusses a laboration on detecting different wavelengths from a UV-c light tube which resulted in activity being detected in the visible light range. The speaker asks if this is due to the quality of the light tube or if there could be collisions between the tube and Monochromator causing a decrease in photon energy. They also inquire about the purple glow of UV light and whether it is from the bulb or the air, and whether the ratio of UV intensity to visible intensity would change with distance. The expert, maimonides, explains that a typical UV-C lamp emits visible light due to the spectral lines of mercury and other gases used in the tube, while a "black light" lamp filters out all visible light. They
  • #1
abotiz
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Hi!
I did a laboration on detecting different wavelenght from a UV-c light tube and the electrometer detected some activity from the Monochromator in the area of visible light (400nm-700nm).
I would like to know if this has something to do with the quality of the light tube? Or does something happen between the light tube and Monochromator that gives some photons less energy, ie collisions in the path to the Monochromator?

Or is it a combination of both?

Also, how come we see the " glow " (the purple glow ) of a UV light, it should not be visible for our eyes. What I mean is, shouldn't the Uv light bulb look like a regular bulb that is not connected to any power source like this one http://www.rapidonline.com/netalogue/zoomed/Large/M077725W01.jpg" [Broken]

Thanks!
 
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  • #2
I think it's from the bulb, but it depends on what type of bulb exactly.

If it was from the air, wouldn't the ratio of uv intensity vs visible intensity change with distance?
 
  • #3
A typical UV-C lamp is a "naked" (quartz glass, no phosphors, no filters) low pressure mercury discharge. Mercury has quite a few spectral lines in the visible range, so what you measure is completely normal. There is probably some Neon/Helium/Argon in the tube to help start the discharge. This will add a few visible spectral lines.
The "black light" lamp in your link has all visible light filtered out; check this http://en.wikipedia.org/wiki/Black_light

maimonides

Take care of your eyes and skin when working with UV-C!
 
  • #4
Thanks maimonides for your reply, it helped me understand a little bit more about the visibile light emitted from the UV-c light tube.
 
  • #5


I can provide some insights into your questions. Firstly, the Monochromator is a device that separates light into its different wavelengths, and it is possible that some visible light is being emitted from the UV-c light tube due to its quality. However, it is more likely that the visible light detected is a result of a phenomenon called fluorescence. When UV light hits certain materials, it can excite electrons and cause them to emit visible light. This is why some objects "glow" under UV light, and it is possible that the materials used in the Monochromator are exhibiting this phenomenon.

As for why we can see the purple glow of a UV light, it is because our eyes are sensitive to a small range of wavelengths, including some UV light. However, our eyes are not as sensitive to UV light as they are to visible light, which is why we do not usually see it. The UV light bulb may not look like a regular bulb because it is designed to emit mostly UV light, which our eyes cannot see. The small amount of visible light that is emitted is likely due to the materials used in the bulb and the fluorescence phenomenon mentioned earlier.

In summary, the visible light detected by the Monochromator is likely a result of fluorescence, and the purple glow of a UV light is a combination of our eye's sensitivity to some UV light and the materials used in the bulb. I hope this helps to answer your questions.
 

1. How does UV light produce visible light?

UV light produces visible light through a process called fluorescence. When UV light interacts with certain materials, it excites their electrons, causing them to jump to a higher energy state. As the electrons return to their original state, they release the excess energy in the form of visible light.

2. Why can't we see UV light with our naked eyes?

Our eyes are only capable of detecting a small portion of the electromagnetic spectrum, known as visible light. UV light falls outside of this range, making it invisible to us. However, some animals, such as bees and birds, have the ability to see UV light.

3. How is UV light different from visible light?

UV light has a shorter wavelength and higher energy than visible light. This means that UV light has a higher frequency and can cause more damage to living organisms. Visible light, on the other hand, has a longer wavelength and lower energy, making it less harmful.

4. Can UV light be harmful to humans?

Yes, UV light can be harmful to humans if we are exposed to it for extended periods. UV light is known to cause sunburns, premature aging of the skin, and can increase the risk of developing skin cancer. It is important to protect ourselves from UV exposure by wearing sunscreen and limiting our time in the sun.

5. How is UV light used in everyday life?

UV light has many practical applications in our daily lives. It is commonly used in sterilization processes, such as in hospitals and water treatment plants, to kill bacteria and other microorganisms. UV light is also used in tanning beds, counterfeit detection, and insect zappers. Additionally, UV light is used in fluorescent bulbs to produce visible light in our homes and offices.

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